Ultrasonic Cleaning Solutions for Metal: The Complete Guide
Cleaning metal parts in an ultrasonic bath is a matching problem. The soil on the part (fabricating and cutting oils, buffing compound, drawing lubricants, heat-treat scale, rust, oxide) and the base metal (steel, aluminum, brass, zinc, magnesium, titanium, stainless) together decide which chemistry cleans fast without etching, pitting, or gassing the part. Reach for a degreaser when the problem is rust and the rust stays. Drop an aluminum housing into a caustic rust stripper and you can damage the part faster than you cleaned it.
The right metal cleaning solution does two things at once: it removes the specific contamination, and it leaves the base metal untouched. That is why Branson formulates separate chemistries for oils, oxides, and rust instead of selling one all-purpose cleaner for every job. This guide covers the three chemistry types behind metal cleaning solutions, how to match the right metal cleaner to your contamination and your base metal, and which Branson concentrate fits each job. Every product referenced is part of the Branson ultrasonic cleaning chemical lineup carried by Process Equipment & Supply, Branson’s largest stocking distributor in the United States and a Branson chemistry specialist serving the industrial, medical, and laboratory markets since 1970.
Quick selector. Match the soil to the chemistry first, then check the metal:
- Oils, greases, cutting fluids, and lubricants: an alkaline metal degreaser (MC-1, MC-2, MC-3, or IS).
- Rust, oxide, tarnish, and light scale: acidic OR Oxide Remover.
- Heavy rust, scale, paint, or baked carbon on ferrous parts: caustic LRS Liquid Rust Stripper.
- Soft or mixed metals present (aluminum, magnesium, zinc): stay with an aluminum-safe alkaline cleaner (MC-1 or MC-3).
Why Metal Cleaning Is a Matching Problem
The cleaning chemistry that strips rust off cast iron will dissolve an aluminum casting. The degreaser that floats cutting oil off steel will leave oxide untouched. Two variables drive every metal cleaning decision: what is on the part, and what the part is made of.
Contamination type. Industrial metal soils fall into a few groups, and each one points to a different chemistry. Fabricating, cutting, and polishing oils, drawing lubricants, light carbon, and general shop grime are organic soils that alkaline degreasers remove. Rust, tarnish, oxide, and heat-treat scale are inorganic and need an acid or a caustic to break them down. Buffing and polishing compound is its own category with a dedicated remover. A part can carry more than one of these at once, which is why heavy operations often run a degreasing step and a de-rusting step in sequence rather than expecting one tank to do both.
Base-metal sensitivity. Ferrous metals (carbon steel, cast iron) and stainless steel tolerate a wide range of chemistry. The reactive metals (aluminum, magnesium, and zinc) do not. Acidic and caustic solutions attack them, and the reaction can release free hydrogen when the solution contacts a reactive metal. Brass, copper, titanium, and tin sit in between and depend on the specific formulation. The practical rule: identify the most reactive metal in your load first, then choose a chemistry that protects it.
The cost of getting the match wrong is not just a part that comes out dirty. It is etching, pitting, discoloration, hydrogen risk on reactive metals, and flash rust on freshly cleaned steel. Matching chemistry to the job avoids all of it.
The Three Chemistry Types for Ultrasonic Metal Cleaning
Nearly all metal cleaning runs on three chemistry families. Most shops use one alkaline degreaser as the workhorse and keep an acidic or caustic option for rust and scale.
Alkaline Cleaners: Oils, Greases, and General Soils
Most metal cleaning is degreasing, and alkaline chemistry handles it. There are two mechanisms. Emulsifying cleaners hold the soil in solution and keep it from redepositing on the part, which suits parts that go straight to the next operation. Displacing cleaners float the soil to the surface so it can be skimmed off, which extends bath life on heavy oil loads. Branson’s alkaline metal concentrates are biodegradable, phosphate-free, and caustic-free, and they cover the MC-1, MC-2, and MC-3 metal cleaners, IS Industrial Strength, and the lighter-duty GP General Purpose and DP2300 powder. They run anywhere from ambient up to 180 degrees F depending on the product, and heat speeds the chemistry. These are the Branson metal degreasers most shops reach for first.
Acidic Cleaners: Rust, Oxides, and Scale
When the problem is rust, tarnish, oxide, or heat scale rather than oil, choose a formulation intended for those deposits. Alkaline degreasers and caustic rust strippers serve different tasks. OR Oxide Remover is a blend of non-ionic detergents in an acidic base that rapidly strips rust and oxides, and it is the standard choice for cleaning up after soldering, brazing, and welding. Because acidic solutions attack the reactive metals, OR is for steel, stainless, brass, and copper, not for aluminum, magnesium, or zinc.
Caustic Strippers: Heavy De-Rusting, De-Scaling, and Paint
The heaviest jobs call for a caustic stripper. LRS Liquid Rust Stripper is a double-chelated, highly caustic, non-foaming concentrate built for de-rusting and de-scaling ferrous metal, paint stripping, injection-mold cleaning, and removing baked carbon from engine parts. It is the most aggressive chemistry in the line and is reserved for ferrous metals. It attacks aluminum, zinc, and magnesium, so reactive metals never go in an LRS bath.
How to Choose: Match Contamination and Metal to the Right Cleaner
Two questions narrow the selection to a single product.
What is the contamination? Oils, greases, and lubricants point to an alkaline cleaner (the MC series or IS). Rust, oxide, and scale point to acidic OR for routine oxide removal, or caustic LRS for heavy de-rusting and de-scaling. Buffing and polishing compound points to BC Buffing Compound. Light, mixed general soils on non-critical parts can use GP or the DP2300 powder.
What is the base metal? This is the constraint that overrides everything else. If aluminum, magnesium, or zinc is present, acidic and caustic chemistries are off the table, and you select an aluminum-safe alkaline cleaner (MC-1 or MC-3). Ferrous and stainless parts tolerate the full range. Brass, copper, and tin should be checked against the compatibility chart below before you commit. When a basket holds mixed metals, clean to the most reactive metal in the load, not the toughest soil.
For broader chemistry context across the full Branson lineup, including the general-purpose and electronics formulations, see The Complete Guide to Ultrasonic Cleaning Solutions. For PCB and electronic assembly cleaning, which is a separate chemistry problem, see Ultrasonic Cleaning Solutions for Electronics.
The Branson Metal Cleaning Concentrates
Metal Cleaners: MC-1, MC-2, and MC-3
The MC series is the core of Branson’s metal cleaning solutions. All three are alkaline metal cleaners, biodegradable, phosphate-free, and caustic-free, mixed at 7 to 10% by volume. They differ by cleaning mechanism and, critically, by which metals they are safe on.
MC-1 Metal Cleaner is a displacing cleaner that carries soil to the surface for removal by skimmer or by hand. It removes fabricating, cutting, and polishing oils and greases and is the broadest-compatibility cleaner in the line, showing no effect on any metal in the compatibility chart below, including aluminum, magnesium, and zinc. It runs from ambient to 120 degrees F. MC-1 is the choice when you want to skim oil off the bath and you have soft or mixed metals in the load.
MC-2 Metal Cleaner is an emulsifying cleaner for general-purpose and maintenance degreasing. It holds soils in solution to prevent redeposit and removes oils and greases from ferrous metals, stainless steel, titanium alloys, copper, and copper alloys. It is not recommended for aluminum or aluminum alloys. It runs from ambient to 180 degrees F.
MC-3 Metal Cleaner is the heavy-duty emulsifying cleaner to use when you need an emulsifier and aluminum is present. It removes oils, greases, and a wide range of soils and is safe on aluminum and aluminum alloys. It runs from ambient to 160 degrees F.
The quick rule: aluminum in the basket points to MC-1 or MC-3; routine ferrous and stainless maintenance degreasing points to MC-2.
IS Industrial Strength
Branson IS Industrial Strength is the heavy-duty alkaline degreaser in the metal line, for the dirtiest organic soils on metal parts. It readily removes heavier greases and oils, particulate, drawing lubricants, and light carbon deposits. Typical applications include cleaning heavier soils off automotive, aircraft, and similar mechanical components, and cleaning parts prior to secondary finishing such as painting, plating, and electrostatic coating. IS is mixed at 8 to 10% by volume and runs from ambient to 180 degrees F. It can cause a slight etch on aluminum, so test aluminum parts before committing a production load.
OR Oxide Remover
OR Oxide Remover is the acidic option for rust and oxide removal. As a metal oxide remover, it rapidly strips rust and other oxides and is the standard cleanup for oxide formed during soldering, brazing, and welding. OR is mixed at 6 to 7% by volume and runs from ambient to 120 degrees F. As an acidic chemistry it is for steel, stainless, brass, and copper. It attacks aluminum, magnesium, and zinc, so reactive metals stay out of an OR bath.
LRS Liquid Rust Stripper
LRS Liquid Rust Stripper is the caustic heavy-hitter: double-chelated, highly caustic, and non-foaming. It handles de-rusting and de-scaling of ferrous metals, paint stripping, and heavy degreasing. Typical jobs include injection-mold cleaning, removing non-pitted rust from ferrous parts, stripping baked carbon from internal combustion engine components, and cleaning food-processing equipment. LRS is mixed into cool water at 4 to 8 ounces per gallon and operated at 160 to 180 degrees F. It is for ferrous metals only and attacks aluminum, zinc, and magnesium.
Passivation: PE-120 Citric Acid Passivate
Passivation is a finishing step, not a degreaser. After stainless steel is cleaned or machined, passivation removes free iron and restores the corrosion-resistant chromium-oxide layer. For citric-acid passivation, Process Equipment & Supply carries PE-120 Citric Acid Passivate Cleaner, a 10% citric solution and a lower-toxicity alternative to nitric-acid baths. Citric passivation is commonly run as a heated immersion or ultrasonic step. Validate the process against the applicable standard, such as ASTM A967, before production use.
Alkaline vs. Acidic vs. Caustic: When to Use Each
| Chemistry | Removes | Products | Use on | Avoid on |
|---|---|---|---|---|
| Alkaline | Oils, greases, lubricants, general soils | MC-1, MC-2, MC-3, IS, GP, DP2300 | Most metals (check per product) | Aluminum with MC-2 or IS (etch) |
| Acidic | Rust, oxide, tarnish, light scale | OR Oxide Remover | Steel, stainless, brass, copper | Aluminum, magnesium, zinc |
| Caustic | Heavy rust, scale, paint, baked carbon | LRS Liquid Rust Stripper | Ferrous metals | Aluminum, zinc, magnesium |
Solution Effects on Metals
This compatibility reference is published by Branson and appears on every chemistry product page. Check it before running a new metal in a given chemistry. A note on terminology: LRS is a caustic, meaning a strongly alkaline chelating stripper. Branson’s chart groups it with the alkaline products, while its product description calls it highly caustic. This guide labels it caustic to flag its strength and stricter handling.
| Cleaner | Steel | Brass | Aluminum | Magnesium | Zinc | Stainless / Copper | Tin |
|---|---|---|---|---|---|---|---|
| MC-1 (alkaline) | None | None | None | None | None | None | None |
| MC-2 (alkaline) | None | None | Slight etch | None | None | None | None |
| MC-3 (alkaline) | None | None | None | None | None | None | None |
| IS (alkaline) | None | None | Slight etch | None | None | None | None |
| OR (acidic) | None | None | Slight attack | Attacks | Attacks | None | None |
| LRS (caustic) | None | None | Attacks | Attacks | Attacks | None | Slight attack |
Notes:
- Tin: no effect if the solution temperature is below 140 degrees F.
- Some aluminum alloys may show a slight etch.
- Free hydrogen may be released if an acidic or caustic solution contacts a reactive metal (aluminum, magnesium, zinc).
- When in doubt, run a test sample before committing a production load.
Using Metal Cleaning Chemicals in an Ultrasonic Bath
The numbers below are starting points. Validate against your actual parts, soil, and metal before locking in a production process.
Dilution. Follow the concentration on each product: 7 to 10% for the MC series, 8 to 10% for IS, 6 to 7% for OR, and 4 to 8 ounces per gallon for LRS. Mixing weaker than the label slows cleaning more than it saves on concentrate.
Temperature. Heat increases the chemical activity of every solution, and the alkaline degreasers reward running hot (up to 180 degrees F for MC-2 and IS, 160 for MC-3, 120 for MC-1). OR runs ambient to 120 degrees F. LRS is mixed into cool water and then operated at 160 to 180 degrees F. Bring the bath to temperature before loading parts, because cold solution dampens cavitation.
Degas. Run a fresh, heated bath empty for 5 to 10 minutes before the first load. Fresh solution holds dissolved gas that absorbs cavitation energy, and degassing measurably improves first-batch consistency.
Cycle time. Start at 5 to 10 minutes and adjust to the soil. Heavy grease, scale, or rust takes longer; light maintenance degreasing takes less.
Rinse and flash rust. Rinse parts after the cycle. After an acidic OR or caustic LRS step, rinse and dry steel promptly, because freshly stripped steel will flash-rust in minutes. A clean-water or alkaline follow-rinse and prompt drying prevent it.
Mixed-metal loads. Clean to the most reactive metal in the basket. If aluminum is present, an acidic or caustic chemistry is out regardless of what the steel needs.
Bath maintenance. Change the solution when cleaning times climb or quality drops. Suspended soil coats the tank bottom and dampens ultrasonic action. With a displacing cleaner like MC-1, skim the floated oil to extend bath life.
Equipment. These chemistries run in any ultrasonic tank that holds the operating temperature and produces consistent cavitation, typically at 40 kHz for metal parts. Heated digital units such as the Branson CPX8800H handle benchtop and small-batch work, and industrial-scale tanks cover high-throughput production. Never put alcohol, gasoline, bleach, mineral acids, flammable, semi-aqueous, or combustible liquids in an ultrasonic tank, and never mix chemistries.
Safety and Environmental Profile
The Branson alkaline metal cleaners (MC-1, MC-2, MC-3, IS) are biodegradable, phosphate-free, and caustic-free. OR is acidic and biodegradable, and standard acid-handling precautions apply. LRS is highly caustic and demands gloves, eye protection, and careful handling. For every product, follow the Safety Data Sheet for handling, spill response, and disposal, and never combine these chemistries with each other, with bleach, with mineral acids, or with any solution not approved for ultrasonic use. The SDS for each product is available as a downloadable PDF on its product page. If you are searching for metal cleaning solvents, note that ultrasonic baths use water-based chemistries, not flammable solvents; the Branson metal line delivers solvent-grade results without the fire, fume, and disposal risks.
Two handling notes specific to this line. First, free hydrogen can be released when an acidic or caustic solution contacts a reactive metal, which is one more reason to keep aluminum, magnesium, and zinc out of OR and LRS baths. Second, these chemicals ship by ground only within the continental United States and Canada and cannot be air shipped. Spent solution accumulates dissolved metals and process contamination and falls under industrial wastewater rules in most jurisdictions regardless of the base chemistry’s biodegradability.
The Branson Metal Cleaning Lineup at a Glance
| Product | Type | Primary Application | Concentration | Operating Temperature | Aluminum-Safe |
|---|---|---|---|---|---|
| MC-1 | Alkaline (displacing) | Fabricating, cutting, polishing oils on mixed metals | 7-10% | Ambient-120 °F | Yes |
| MC-2 | Alkaline (emulsifying) | General maintenance degreasing of ferrous, stainless, titanium, copper | 7-10% | Ambient-180 °F | No |
| MC-3 | Alkaline (emulsifying) | Heavy-duty degreasing where aluminum is present | 7-10% | Ambient-160 °F | Yes |
| IS | Alkaline | Heavy greases, oils, particulate; pre-finish cleaning | 8-10% | Ambient-180 °F | Caution (slight etch) |
| OR | Acidic | Rust and oxide removal after weld, braze, solder | 6-7% | Ambient-120 °F | No |
| LRS | Caustic | Heavy de-rust, de-scale, paint strip, mold and engine cleaning | 4-8 oz/gal | 160-180 °F | No |
For lighter or non-metal work, GP General Purpose and the DP2300 powder cover general cleaning, BC Buffing Compound removes polishing and buffing compound, and EC Electronics Cleaner is an aqueous alkaline cleaner for PCBs and electronic assemblies.
Frequently Asked Questions
What is the best ultrasonic cleaner solution for metal parts? For degreasing, an alkaline metal degreaser is the right tool: MC-1 or MC-3 when aluminum is present, MC-2 for ferrous and stainless maintenance, and IS for heavy soils and pre-finish cleaning. For rust and oxide, OR Oxide Remover is the acidic choice, and LRS Liquid Rust Stripper handles heavy de-rusting and de-scaling on ferrous metal. The “best” solution is the one matched to your contamination and base metal.
Should I use an alkaline or acidic cleaner? Alkaline removes oils, greases, and organic soils. Acidic removes rust, oxide, and scale. If the part is oily, start alkaline. If it is rusted or oxidized, you need acidic OR or caustic LRS. Heavily soiled and rusted parts sometimes need both, run as separate steps.
Can I clean aluminum in an ultrasonic bath? Yes, with an aluminum-safe alkaline cleaner. MC-1 and MC-3 are safe on aluminum and aluminum alloys. MC-2 and IS can cause a slight etch, and the acidic and caustic products (OR, LRS) attack aluminum and should never be used on it.
How do I remove rust from metal in an ultrasonic cleaner? Use OR Oxide Remover for light rust and oxide, including cleanup after welding, brazing, and soldering. For heavy rust, scale, and paint on ferrous parts, use LRS Liquid Rust Stripper. Rinse and dry steel promptly afterward to prevent flash rust.
What is the difference between OR Oxide Remover and LRS Liquid Rust Stripper? OR is a milder acidic cleaner for light rust and oxide on steel, stainless, brass, and copper. LRS is a highly caustic, aggressive stripper for heavy de-rusting, de-scaling, and paint removal on ferrous metals only. OR is the routine choice; LRS is for the heaviest jobs.
Can I clean mixed metals in the same load? Clean to the most reactive metal present. If aluminum, magnesium, or zinc is in the basket, use an aluminum-safe alkaline cleaner and keep acidic and caustic chemistries out. Check the solution-effects chart above before running an unfamiliar combination.
Do these solutions work in non-Branson ultrasonic baths? Yes. They are chemistries, not bath accessories, and work in any ultrasonic tank that holds the operating temperature and produces consistent cavitation, typically at 40 kHz for metal parts.
Ordering and Support
The full Branson metal cleaning chemistry line ships from stock at Process Equipment & Supply, with same-day shipping on orders placed before 2:00 PM EST and free shipping on orders over $125. Chemicals ship by ground only within the continental United States and Canada and cannot be air shipped.
Three ways to take the next step:
- Order direct from the product pages: MC-1, MC-2, MC-3, IS, OR, and LRS. Concentrates ship in quart cases (4, 8, or 12 quarts).
- Request a quote or a sample for process validation before committing to production volumes.
- Download the Safety Data Sheet for any product from its page for compliance and procurement review.
For help matching a chemistry to your metal and contamination, bath sizing, or questions about the full Branson cleaning chemical lineup, contact Process Equipment & Supply at 1-800-539-6336 or sales@proequip.com. ProEquip has carried the Branson line since 1970 and is the largest stocking distributor of Branson equipment in the United States.